In some countries, major rivers – diverted, dammed or over-exploited – no longer reach the sea. Aquifers millennia in the making are being sucked dry. Pollution in many forms is tainting water above ground and below.

Cape Town, though, was not especially beset by any of these problems. Indeed, in 2014 the half-dozen reservoirs that served the South African city’s four million people brimmed with rainwater.

But that was before a record-breaking, three-year, once-every-three-centuries drought reduced them to a quarter capacity or less.

Today, Capetonians are restricted to 50 litres a day (13.2 US gallons) – less than runs down the drain when the average American takes a shower.

Climate scientists foretold trouble, but it arrived ahead of schedule, said Helen Zille, premier of the Western Cape province.

“Climate change was to have hit us in 2025,” she told a local news outlet.

“The South Africa Weather Services have told me that their models don’t work any more.”

Worldwide, the water crises hydra has been quietly growing for decades.

Since 2015, the World Economic Forum’s annual Global Risk Report has consistently ranked “water crises” as among the global threats with the greatest potential impact — above natural disasters, mass migration and cyberattacks.